I am bad at explaining my theories in writing, but I will try my best to explain how I think there will be a new God Valley incident, which I call "Mary Geoise Incident".

In God Valley there was a battle between the Rocks Pirates against the Roger Pirates and the Marines, where the biggest names were Xebec, Roger and Garp, besides these groups there were the World Nobles and some slaves.

In Mary Geoise incident will have Im (The King of the World) replacing Xebec (the one who had the ambition to become the King of the World), we will also have Dragon (Garp's son who is the greatest enemy of the World Government) replacing Garp and Shanks (Roger's adopted son who has already talked to the five elders and I theorize is just waiting for the right moment to attack the World Government) replacing Roger, obviously the subordinates of these three will also be present, and as in God Valley Incident the World Nobles and some slaves (those who have not yet been freed by the revolutionary army) will be present.